<p>This study develops an integrated research framework that combines a Comprehensive Evaluation Indicator System, Coupling Coordination Degree Model, Composite System Evolution Model, and Obstacle Degree Model to analyze the dynamics of the 'Port-Industry-City' system. Using Fangchenggang, a keyt port in western China, as a case study, the paper contributes to the understanding of how port, industry, and city systems interact and evolve over time. The research findings indicate that: (1) At the system level, the coordination and interaction degree consistently improve, although the coupling and coordination exhibit fluctuating trends. The system progresses through various lag types, from port and city lag to industrial lag. (2) At the subsystem level, while the 'Industry-City' system remains stable, the 'Port-City' and 'Port-Industry' systems show fluctuating upward evolution, with U-shaped and W-shaped dynamic patterns. (3) At both the first- and second-level index factors, the primary lagging factors include industrial structure, city scale, and urban economy. Among the secondary indicators, the most significant lagging factors are total highway mileage and resident population. (4) The study highlights that the 'big port, small city' paradigm imposes significant constraints on the integrated development of Fangchenggang, with industrial development being the most critical challenge for future growth. This research provides new insights into the 'Port-Industry-City' literature by developing a multi-dimensional framework to assess the synergistic development of port cities and their industries.</p>